Cap closure seal



n Filed Dec. l, 1937 Kals SJreenhH Patented `lulry 4, 1939 UNITED STATESPATENT OFFICE Application December 1, 1937, Serial No. 177,444 In SwedenDecember 3, 1936 4 Claims.

This invention relates to closure caps for bottles and the like.

In conventional cap closures the circular top portion of the cap istightened with or without insertion of a sealing gasket, against thebottlerim around the mouth. As is easily understood, perfect sealingdepends on the radial width of that annular surface of the cap whichcontacts the bottle-rim and upon the pressure of the cap against thebottle-rim. It is, therefore, of paramount importance for a durablesealing that, after the capping operation, the cap is not displaced crsubject to any deformation impairing the two above mentioned factors.

In the conventional closures the circular top portion of the cap shellis usually plane or slightly convex, Consequently, in a cap shell ofthis type, the top portion offers little resistance to the forces,which, in case of overpressure in the bottle, tend to convex it. If thecontents of the bottle have been introduced under overpressure and thebottle, before use, is stored for some considerable time or is subjectto great variations in temperature, it happens that the upper portionoi' the cap assumes gradually a convex shape. This deforming of the capmay have the effect that the sealing against the bottle-rim is impairedpartly by the reduction of the radial width of the contacting surface,partly by the decrease 30 of the cap pressure against the rim.

The present invention has for its object to improve the said closures inthe respect mentioned preferably by giving both, the bottle-head, ormore particularly the rim thereof around the mouth, and the cap shell,the latter before or during the capping operation, a continuously curvedconvex shape, which corresponds as closely as possible to the convexshape of the cap shell that may arise by the action of the overpressurein the bottle.

The invention is illustratively exemplied in the accompanying drawing,in which:

Figures l and 2 illustrate an embodiment of the invention.

Figure l is an elevation of the bottle neck before application of thecap.

Figure 2 is one half of an axial section on a larger scale through abottle neck with a cap applied thereto.

Figure 3 shows a modied embodiment of the bottlehead, in elevation.

Figure 4 shows a sectional view of a cap of a known initial shape.

As shown in Figures l, 2 and 3 the rim I around the bottle-mouth isconvex so that most of it,

when seen in axial section, approaches a spherical zone'. However, theinvention is not limited to an exactly determined convex shape butincludes all variations similar to the convex shape which a normal capwould assume under overpressure in the bottle. The contour of convexitymay preferably have a radius, which is smaller than the diameter of thecap and the corresponding cross section respectively through thebottle-head, and the center of which is located within the bottle-mouth.The contour` of convexity may also be thought to be composed of severalspherical arcs, provided the contour rises in a continuous curve towardsthe bottle-mouth, as is clearly shown in Figure 2. 'Ihe convexityterminates downwardly on the out-side of the bottle at the edge 2, theso-called sealing edge, with which the cap shell 3 (Figure 2) is, inknown manner brought into engagement, during the capping operation bythe skirt 4 of the cap shell being rolled in below the edge 2 into agroove 8. The said operation is, as usual, performed mechanically,generally by means of an elastic ring, provided in a capping head, whichring is compressed around the bottle-head, while the cap, by a plungeror the like, is pressed against the bottlemouth. The cap thus beingsubjected to a well adapted sealing pressure, it is deformed from itsoriginal shape, shown in Figure 4, under simultaneous shrinking andstretching, to fit snugly over the outer contour of the bottle-head. Acorresponding change of shape is also effected on the sealing insertion5 in the cap shell, in the cases where such insertions are used, seeFigure 2. From Figure 2 it will be seen that the effective tighteningsurface of the rim extends, as shown in section, over the entire radialthickness .6 of the wall of the bottle neck.

To avoid with certainty the deforrnng` of the cap shell by overpressurein the container the `dome-shaped portion of the cap shell should havean altitude substantially equal to the radius of the mouth of thecontainer.

From the foregoing it will be clear that a principal feature of theinvention is to shape the rim of the bottle-neck and the top of the capso as to substantially follow an imagined spherical segment.

The termination of the convex surface by a suitable sealing edge is ofimportance for an effective tightening against the convex rim and theapplication of the cap shell so that the same cannot lift itself fromthe bottle-head after the capping pressure has ceased. For this purposeit is also desirable that the skirt of the cap engage the edge aroundthe bottle-mouth at each point of the edge. To replace the skirt byfingers grasping under the edge, as has previously been proposed, would'not at all suilice for a durable and reliable closure.

In order to obtain this edge the outside of the bottle-head may beshaped in many different Ways. For caps to be removed by being slit up,for example, by means of a tearing tab I3, the bottle-head may be shapedwith a peripheral groove 8, Figure 1, as usual, or with a shoulder I2,according to Figure 3, extending around the mouth.

Finally, it is pointed out that the convexity of the bottle-head is notnecessarily restricted to exactly the above described shape of thebottlehead for making possible the engagement of the cap shell; othersuitable shapes may be used Within the scope of the present invention.

Of course, it is possible, when manufacturing the cap, to give to itstop the required convex shape.

The combination of a convex bottle neck rim with a cap having a.dome-shaped top portion may also be used Without a sealing insertion.

Having now described my invention, what I claim as new and desire tosecure by Letters Patent is:

1. In combination with a bottle neck, a closure cap comprising acontinuously curved domeshaped top portion having its greatest innerperiphery in contact with the greatest outer periphery of the bottleneck, said dome-shaped cap portion having an altitude substantiallyequal to the inner radius of the mouth of the bottle neck and beingsupported over the entire radial thickness of the Wall of the bottleneck.

2. A combination, as claimed in claim l, in which the greatest innerperiphery of said dome- `shaped cap portion contacts the greatest outerperiphery of the bottle neck in a horizontal plane below the level ofthe mouth of the bottle neck.

3. A combination, as claimed in claim 1, in which the upper rim of thebottle neck has a curved shape substantially corresponding to the innersurface of said dome-shaped cap portion.

4. A combination, as claimed in claim 1, comprising further a sealinginsertion between the upper rim of said bottle neck and said domeshapedcap portion, the upper surface of said sealing insertion having a shapesubstantially corresponding to the inner surface of said domeshaped capportion.

ROLF STEENHOFF.

